|Politecnico di Torino|
|Academic Year 2016/17|
Automotive fluid power systems
Master of science-level of the Bologna process in Automotive Engineering - Torino
The module presents and examines automotive fluid power components and systems in terms of their graphical symbols, layout, specific features, construction and operation. Students learn how to identify and interpret fluid power circuits, comprehend and explain their purpose in relation with their constitutive components. Aim of the course is to acquaint students with methods for the analysis and critical evaluation of fluid power components and systems specific to automotive applications.
Expected learning outcomes
Foreword: aim of a fluid power system is to transfer power through a working fluid. In the automotive field, typical applications are steering units, breaking systems, active suspensions, variable valve actuation and much more.
The design, development, testing and production of fluid power components or systems require very specific competencies, but the prerequisite is a strong and solid knowledge of the basic principles governing the generation and the control of the hydraulic power and the mutual interaction among the components.
In this context, the knowledge acquired by the students upon completion of this course involves:
• to interpret a simple fluid power scheme according to the ISO standard 1219,
• to identify the main fluid power components, their specific function and operation,
• to know the fundamental equations for the evaluation of the flow rate, pressure, speed, torque and power,
• to identify and quantify the sources of power dissipation in a fluid power system and evaluate the efficiency,
• to learn the working principle of the main automotive fluid power systems and components,
• to learn the basics of some commercial tools for the simulation of fluid power circuits.
With the skills acquired during the course, students should be able to:
• design a simple layout of a fluid power system,
• select and size the correct component (pump, actuator, valve) to achieve a specified function,
• analyse qualitatively and quantitatively the different working modes of a fluid power circuit,
• understand the working principle of the following fluid power systems:
o hydraulic steering units for passenger cars and off-road vehicles,
o electrohydraulic breaking systems,
o closed circuit hydrostatic transmissions,
o lubricating circuits for internal combustion engines.
Prerequisites / Assumed knowledge
Awareness of concepts covered in Physics, Fluid Mechanics, 3D Modelling.
• Fundamentals of Fluid Power (8 hours).
• Positive displacement pumps and motors (8 hours): different designs, real steady-state characteristics flow-pressure and flow-speed, instantaneous flow rate and torque, volumetric and mechanical-hydraulic efficiencies, flow and torque losses models, evaluation of the displacement. Controls for displacement variation.
• Fluid Power valves (6 hours): on-off directional control valves; flow and pressure control valves (pressure relief, pressure reducing, two-port and three-port flow control), single and double stage; ideal and real performance characteristics; analysis of real components.
• Accumulators (1 hour): types and their dimensioning criteria.
• Flow generating units (7 hours): constant and variable flow rate, for open and closed circuits; constant pressure; ideal and real performance characteristics.
• Hydrostatic transmissions (4 hours): transmission ratio and torque ratio, characteristics of primary variable-secondary fixed, primary fixed-secondary variable, primary variable-secondary variable versions, total efficiency, corner power and torque conversion range.
• Hydrostatic steering systems for passenger cars and off-road vehicles (8 hours): working principles, mechanical position feedback, analysis of sections of the rotating directional control valves, fixed and variable displacement pumps.
• Hydrostatic braking systems (7 hours): brake booster, vacuum pump, tandem master cylinder, ABS modules (from 2S to 8). The ESP integration for lateral stability.
• Hydraulic valve train (1 hour): hydraulic lash adjusters, variable valve actuation.
• ICE lubrication systems (10 hours): layout (wet and dry sump solutions), oil path and pressure distribution inside the crankshaft; journal bearings: pressure distribution (Sommerfeld and Ockvirk bearings), load capacity, through flow; cooling jets; fluid conditioning group; lubricating pumps, fixed and variable displacement, with discrete pressure controls; evaluation of the pressure and flow rate through the circuit as function of oil temperature and engine speed. Basic properties of the lubricants.
During the semester, five numerical exercises will be progressively proposed on the Didactic Web Portal of the Politecnico. This homework must be downloaded and solved individually, according to explicit rules, by all students. The purpose of the homework is twofold: a self-assessment of acquired knowledge and competence; a training route toward the final written test. When successfully registering the exam, students must hand in the complete set of their own homework.
Two sessions of mandatory laboratory work (1.5 hours each) are carried out at the Fluid Power Research Laboratory (Main Campus):
• Pumps, motors and linear actuators: various positive displacement pumps and motors (external and internal gear, axial and radial piston and vane machines) of different manufacturers are disassembled, analysed and contrasted to understand and appraise their peculiarities and mode of operation.
• Steering servo systems and electro-hydraulic braking systems: the main components are disassembled and analysed.
Four sessions of mandatory simulation work (1.5 hours each) are carried out. Briefly introducing simulation environments, problems in modelling and simulation of simple components and systems are presented. Students have the opportunity to perform simulations to gain direct experience of the approach and gain perception of the involved potentials.
A written report about the simulation experiences must be prepared and presented at the examination.
Texts, readings, handouts and other learning resources
In order to avoid students to print on their own the didactic material, the entire set of slides used in lectures in high quality B/W printed form will be available at the beginning of the didactic term:
• Nervegna, N., Rundo, M.: Automotive Fluid Power Systems, Politeko, Torino
Moreover, the slides (with possible minor updates) will be progressively made available only to enrolled students on the Didactic Web Portal in the colour version.
For additional insight into specific topics, reference is made to the following material (in Italian):
• Nervegna, N.: Oleodinamica e pneumatica: Sistemi. Vol. 1, Politeko, Torino
• Nervegna, N.: Oleodinamica e pneumatica: Componenti. Vol. 2, Politeko, Torino
• Nervegna, N.: Oleodinamica e pneumatica: Esercitazioni. Vol. 3, Politeko, Torino
• Gilardino, L.: Esercizi di Oleodinamica, Clut, Torino
Some additional information (bibliography, links, animations) can be found on the official web site of the Fluid Power Laboratory (http://www.fprl.polito.it).
Assessment and grading criteria
The final exam is grounded on a two-hour written test involving numerical evaluations on a proposed problem as well as theoretical questions on concepts and principles exposed during the lectures and laboratory sessions. The test is a "NO BOOK EXAM": the use of personal notes, books and manuals in any form (hard copies and electronic versions) is strictly forbidden. The use of an English dictionary is allowed.
Some examples of written tests will be available on the Didactic Web Portal before the end of the course.
For those who reach in the written test a mark in the range:
• above 20/30 the oral examination is optional,
• from 15/30 to 20/30 an additional oral examination is required to pass the exam,
• below 15/30 the exam is failed.
In case of oral exam, the final mark will be the average between oral and written exams. If the combined mark is < 18/30 the exam is failed and it will be necessary to retake the written test, otherwise the exam is passed.
The oral exam will focus on lectures, laboratory topics and homework.
The oral exam can be required, regardless of the mark of the written test, in case of:
• unjustified absences in the mandatory laboratory/simulation experiences,
• suspicion of student misconduct during the written test.
Programma definitivo per l'A.A.2016/17